The performance did not take place quite in the manner Yo-Yo Ma had envisioned for the young members of the Civic Orchestra of Chicago. But that was much less important than the skills the newly empowered players took away from the experience. And the musical results from the audience's standpoint were little short of amazing.

Monday night's concert by the Chicago Symphony's training orchestra was the culmination of seven months of intensive rehearsals led by Ma, the famed cellist and CSO creative consultant, along with Civic principal conductor Cliff Colnot. Orchestra Hall was sold out for the event. A buzz of anticipation was in the air.

Ma's bold plan was to have these young pre-professional players perform Beethoven's "Pastoral" Symphony from memory and without a conductor. With the safety net thus removed, he told them, they could take collective control of a masterpiece, "own" it in a truly collaborative way that would enable them to listen to each other more acutely than would ordinarily be the case.

A risky challenge for any orchestra, to be sure, but the Civic members were game to take it on. Mentor-in-chief Ma was confident they had the chops to bring it off.

They managed the better part of the dare on Monday evening, transforming the Beethoven Sixth into a piece of enlarged chamber music for 85 orchestral players. No conductor was present and none was needed, save perhaps to shore up a few details and impose a more sharply defined interpretation on the whole.

But the degree of precision, the refinement and blending of sound, the quickness with which the players responded to and interacted with one another – these things would do credit to many an adult professional orchestra. You could see and hear each member of each section giving his or her all, making music rather than just notes.

The one departure from the announced format was that the Civic members were allowed to play with the sheet music in front of them.

Late in the rehearsal process, it was decided that removing the music entirely, on top of going without a conductor, "would result in an unfinished product," Colnot explained after the concert. Some players nevertheless had committed their parts entirely to memory, and I spotted many of them maintaining eye contact with each other throughout the performance, per Ma's game plan.

In retrospect, it was probably the right decision to allow the players to use music if they needed it. Beethoven's music is challenging enough to perform without the firm hand of a conductor at the helm. Why add unnecessary complications?

Ma did not reply to requests for comment.

After remarks to the audience in which the cellist praised the Civic musicians and the CSO support structure in general, he took the primus inter pares role in a stylishly classical reading of Haydn's Cello Concerto in C major. Once again no conductor was used nor was one required, given the intimate scale of the performance. The Civic players took their cues from Ma's golden tone, singing lines and elegant articulations, making the concerto a lively and civilized conversation among friends. When it was over, a beaming Ma bestowed hugs on every first-stand player in his vicinity.

The concert, part of the CSO's ongoing "Rivers" festival, opened with a nature piece that dates from roughly 172 years after the Beethoven symphony – John Luther Adams' "A Northern Suite." A 2004 revision of music Adams had composed decades earlier, the five sections evoke the icy allure of the stark Alaskan terrain he calls home. Here a conductor is needed to bring out the full force of Adams' instrumental subtleties, which Colnot did with complete assurance.

Yo-Yo Ma will be joined by members of the Chicago Symphony Orchestra and the Civic Orchestra for a chamber music program of Bach, Dvorak and Beethoven works, at 8 p.m. Wednesday at Symphony Center, 220 S. Michigan Ave.; $75-$194; 312-294-3000, cso.org.